The present invention generally relates to position location systems, and more particularly, to a vehicle position location system employing enhanced position location processing.
To efficiently manage its resources, a host community needs to have accurate and timely knowledge of the location of its vehicles and personnel. Such vehicles include emergency units (police and fire), trucks, buses, disabled or stolen automobiles, locomotives, box cars, coastal vessels, etc. This data may be combined with current assignment information and displayed for the benefit of supervisory personnel at a single or multiple central locations. Today's existing navigational aids are not well suited to this application because the location is calculated and displayed in the vehicle rather than at the central control point. A separate communications link then has to be provided to relay the positions back to the central facility. In environments consisting of large numbers of vehicles, the time to obtain reliable position fixes on all units of interest is typically excessive.
Previous location systems have been developed which are described in U.S. Pat. Nos. 4,740,792, and 3,714,573, for example, which disclose satellite-based and land-based systems, respectively. Such previous systems employ a basic set of equations to calculate a transmitter's location using the minimum required data with no additional processing. This minimum processing often results in severe error in the computed position. In addition, systems that attempt to use all received data with no preprocessing generally take excessive time to compute a single position. These systems become heavily backlogged when attempting to locate large numbers of transmitters.
Therefore, there is a need for an improved vehicle location system having enhanced vehicle location processing that circumvents the problems of prior systems.